Brake unit of a slip-controlled motor vehicle brake system with a fluid supply device

Abstract

A brake unit of a slip-controlled motor vehicle brake system with a fluid supply device with an electrically operated fluid supply device provides a pressurised hydraulic or pneumatic fluid in the brake circuits of the brake system. The fluid supply device has a pressure chamber with at least one fluid inlet and at least one fluid outlet. One non-return valve each is provided at the fluid inlet and the fluid outlet. A piston which protrudes into the pressure chamber is movable at least into one of two end positions by means of an electric drive device. In the one end position, a minimum volume is defined by the pressure chamber and the piston. In the other end position, a maximum volume is defined by the pressure chamber and the piston.

1 . A brake unit of a slip-controlled motor vehicle brake system with a fluid supply device with an electrically operated fluid supply device for providing a pressurised hydraulic or pneumatic fluid in order to change the pressure in the brake circuits of the brake system, with the fluid supply device comprising
 a pressure chamber with at least one fluid inlet and at least one fluid outlet,   one non-return valve each at the fluid inlet and the fluid outlet,   a piston which protrudes into the pressure chamber and which is movable at least into one of two end positions by means of an electric drive device, with a minimum volume being defined in the one end position by the pressure chamber and the piston, and in the other end position a maximum volume being defined by the pressure chamber and the piston,   wherein the electric drive device is to be supplied with control signals by an electronic control device (ECU), which determine the amplitude, the frequency and/or the duty cycle of the piston stroke,   a spring pressure accumulator upstream of the non-return valve at the fluid inlet, which has a predetermined resonance frequency and is adapted to alternate between a great fluid volume accommodated therein and a small fluid volume accommodated therein, wherein   the electronic control device (ECU) feeds the electric drive device with control signals in such a manner that the piston in the pressure chamber oscillates with the spring pressure accumulator and with a great fluid volume in the spring pressure accumulator sucks in fluid therefrom into the pressure chamber.   
   
   
       2 . The brake unit according to  claim 1 , wherein
 the spring pressure accumulator is adapted for the accommodation of a fluid volume which is almost equal to or greater than the maximum volume which is defined by the pressure chamber and the piston.   
   
   
       3 . The brake unit according to  claim 1 , wherein
 the electric drive device, the piston, and the pressure chamber have a resonance frequency which ranges from 0.8 times to 1.2 times the resonance frequency of the pressure accumulator.   
   
   
       4 . The brake unit according to  claim 1 , wherein
 the electronic control device (ECU) supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber oscillates at a frequency ranging from 0.8 times to 1.2 times the resonance frequency of the spring pressure accumulator.   
   
   
       5 . The brake unit according to  claim 1 , wherein
 the electronic control device (ECU) supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber starts to oscillate from its minimum to its maximum volume when the spring pressure accumulator contains between 80 percent and 100 percent of its maximum fluid volume.   
   
   
       6 . The brake unit according to  claim 1 , wherein
 the electronic control device (ECU) supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber oscillates to the spring pressure accumulator at a phase offset of 150° to 210°.   
   
   
       7 . The brake unit according to  claim 1 , wherein
 the electronic control device (ECU) supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber is in the or near the position of its maximum volume until the non-return valve between the spring pressure accumulator and the pressure chamber is closed.   
   
   
       8 . The brake unit according to  claim 1 , wherein
 the electric drive device comprises an electromagnet arrangement with a stator and an armature.   
   
   
       9 . The brake unit according to  claim 1 , wherein
 the electric drive device comprises an electromagnet arrangement with a stator and an armature, with
 the stator being configured as a multipole stator with several stator poles, and excitation coils which are allocated the respective stator poles, and/or 
 the armature being configured as a multipole armature whose armature poles are aligned to the respective stator poles. 
   
   
   
       10 . The brake unit according to  claim 8 , wherein
 the electromagnet arrangement comprises a working air gap between the stator and the armature, which is preferably oriented transversely to the direction of the movement of the armature.   
   
   
       11 . The brake unit according to  claim 8 , wherein
 the stator comprises two multipole stators which are arranged at an axial distance from each other and which accommodate a multipole armature between them which, during operation, is cyclically attracted by the two multipole stators in order to move the piston between its two end positions in the pressure chamber.   
   
   
       12 . The brake unit according to  claim 8 , wherein
 the armature is connected with the movable piston or is a part of it.   
   
   
       13 . The brake unit according to  claim 8 , wherein
 the pressure chamber, the piston, and the electromagnet arrangement are formed as a preassembled assembly which may be handled as one unit which is to be installed into a correspondingly formed recess in the brake unit.   
   
   
       14 . The brake unit according to  claim 8 , wherein
 two separate pump systems are provided which are to be controlled in phase opposition, each of which being formed by a pressure chamber, a piston, and an electromagnet arrangement as well as non-return valves which are provided at the inlet and the outlet.   
   
   
       15 . The brake unit according to  claim 1 , wherein
 the drive device comprises an eccentric drive which acts on a piston protruding into the pressure chamber, which is movable into at least one of two end positions, with a minimum volume being defined in the one end position by the pressure chamber and the piston, and in the other end position a maximum volume being defined by the pressure chamber and the piston.   
   
   
       16 . A method for operating a brake unit of a slip-controlled motor vehicle brake system with a fluid supply device with an electrically operated fluid supply device for providing a pressurised hydraulic or pneumatic fluid in order to change the pressure in the brake circuits of the brake system, with the fluid supply device comprising a pressure chamber with at least one fluid inlet and at least one fluid outlet, one non-return valve each at the fluid inlet and the fluid outlet, a piston which protrudes into the pressure chamber and which is movable at least into one of two end positions by means of a drive device, with a minimum volume being defined in the one end position by the pressure chamber and the piston, and in the other end position a maximum volume being defined by the pressure chamber and the piston, wherein the drive device is supplied with control signals by an electronic control device, which determine the amplitude, the frequency and/or the duty cycle of the piston stroke, a spring pressure accumulator upstream of the non-return valve at the fluid inlet, which has a predetermined resonance frequency and is adapted to alternate between a great fluid volume accommodated therein and a small fluid volume accommodated therein, wherein the electronic control device feeds the drive device with control signals in such a manner that the piston in the pressure chamber oscillates with the spring pressure accumulator and with a great fluid volume in the spring pressure accumulator sucks in fluid from the spring pressure accumulator into the pressure chamber. 
   
   
       17 . The method according to  claim 16 , wherein the spring pressure accumulator accommodates a fluid volume which is almost equal to or greater than the maximum volume which is defined by the pressure chamber and the piston. 
   
   
       18 . The method according to  claim 16 , wherein the drive device, the piston, and the pressure chamber have a resonance frequency which ranges from 0.8 times to 1.2 times the resonance frequency of the pressure accumulator. 
   
   
       19 . The method according to  claim 16 , wherein the electronic control device supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber oscillates at a frequency ranging from 0.8 times to 1.2 times the resonance frequency of the spring pressure accumulator. 
   
   
       20 . The method according to  claim 16 , wherein the electronic control device supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber starts to oscillate from its minimum to its maximum volume when the spring pressure accumulator contains between 80 percent and 100 percent of its maximum fluid volume. 
   
   
       21 . The method according to  claim 16 , wherein the electronic control device supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber oscillates to the spring pressure accumulator at a phase offset of 150° to 210°. 
   
   
       22 . The method according to  claim 16 , wherein the electronic control device supplies the electric drive device with control signals in such a manner that the piston in the pressure chamber is in the or near the position of its maximum volume until the non-return valve between the spring pressure accumulator and the pressure chamber is closed. 
   
   
       23 . The method according to  claim 16 , wherein the resonance frequency of the respective system is determined by changing the control frequency of the control signals for the electric drive device between a low frequency of approx 10 Hz and a high frequency of approx. 10 kHz, until the fluid stream which is ejected from the pressure chamber is at its maximum. 
   
   
       24 . Use of a brake unit of a slip-controlled motor vehicle brake system with a fluid supply device to be operated electrically for providing a pressurised hydraulic or pneumatic fluid for changing the pressure in the brake circuits of the brake system, with the fluid supply device comprising
 a pressure chamber with at least one fluid inlet and at least one fluid outlet,   one non-return valve each at the fluid inlet and the fluid outlet,   a piston which protrudes into the pressure chamber and which is movable at least into one of two end positions by means of an electric drive device, with a minimum volume being defined in the one end position by the pressure chamber and the piston, and in the other end position a maximum volume being defined by the pressure chamber and the piston,   wherein the electric drive device is to be supplied with control signals by an electronic control device (ECU), which determine the amplitude, the frequency and/or the duty cycle of the piston stroke,   a spring pressure accumulator upstream of the non-return valve at the fluid inlet, which has a predetermined resonance frequency and is adapted to alternate between a great fluid volume accommodated therein and a small fluid volume accommodated therein, wherein   the electronic control device (ECU) feeds the electric drive device with control signals in such a manner that the piston in the pressure chamber oscillates with the spring pressure accumulator and with a great fluid volume in the spring pressure accumulator sucks in fluid therefrom into the pressure chamber.